/* =============================================================
 * Your Grandmother's guide to Algorithms
 * =============================================================
 *
 * Copyright (c) 2007, Saverio Miroddi
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 * 
 *     * Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright 
 *       notice, this list of conditions and the following disclaimer in the 
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the SaverioMiroddiSoftware nor the names of its 
 *       contributors may be used to endorse or promote products derived from 
 *       this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER 
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *  
 * ---------------------------
 * AbstractElement.java
 * ---------------------------
 *
 */
package btree;

/**
 * Data structure for internal node value element, composed of value and node pointer.
 * <br>
 * This class highlight the interesting OO-problem of impossibility to implement a full
 * compareTo when having a hierarchy; in this case we miss the transitivity, but it's not
 * important.
 */
@SuppressWarnings("unchecked")
public class AbstractElement implements Comparable<AbstractElement>
{
	public static final NodeElement NULL_ELEMENT = null;

	public Comparable value;

	public AbstractElement(
			Comparable value)
	{
		if (value instanceof AbstractElement) throw new IllegalArgumentException(value.getClass().toString());
		
		this.value = value;
	}

	public AbstractElement(
			AbstractElement element)
	{
		this(element.value);
	}

	public final int compareTo(
			AbstractElement other) 
	{
		if (value == null && other.value == null)
			return 0;
		else if (value == null)
			return -1;
		else if (other.value == null)
			return +1;
		else
			return value.compareTo(other.value);
	}
	
	@Override
	public String toString()
	{
		return (value == null) ? ("*") : ("" + value);
	}
}
